Unreal Engine vs Bevy

Agent access

1. ai-native userPoint an agent at llms.txt or agent-oriented docs

   weight 2 · round drawn
   Unreal Engine—none0/10

   A direct probe found no llms.txt on Epic's domains, and appending .md to docs URLs returns the HTML SPA shell rather than agent-readable markdown, meaning there is no mechanism to point an agent at machine-readable docs.

   • [probe] “PROBE runtime negative (recorded 2026-09-15): Unreal is the least machine-readable presence of the eight — api.github.com/repos/EpicGames/Un…”

   proof ↗⚑ flag

   Bevy—none0/10

   Direct probes confirm no llms.txt exists (404) and no agent-oriented docs endpoint is served; docs.rs/crates.io provide standard human docs but nothing tailored for agent consumption per the story.

   • [probe] “PROBE llms.txt: HTTP 404 at https://bevy.org/llms.txt”
   • [probe] “PROBE docs-md: HTTP 404 at https://bevy.org/learn/.md”
   • [probe] “PROBE runtime negative (recorded 2026-09-15): bevy.org serves no llms.txt (HTTP 404; docs.rs likewise) and no official MCP exists — communit…”

   proof ↗⚑ flag

2. ai-native userRun the product headlessly / in CI for automation

   weight 2 · round to Unreal Engine
   Unreal Engine~partialprobed6/10

   Docs show real automation building blocks: command-line launch arguments (unreal-docs-7, unreal-docs-14), UAT commands for cooking/packaging/deploying (unreal-docs-16, unreal-docs-17), and Python editor scripting for automating asset tasks (unreal-docs-4), all of which are commonly used to run Unreal headlessly in CI pipelines. However, there is no explicit first-party 'headless mode' or CI-integration guide, and the probe notes Unreal's docs/repos are largely non-machine-readable (403s, no llms.txt, no official MCP), suggesting automation setup requires manual/expert configuration rather than a turnkey CI story. Missing for 10: dedicated headless-mode documentation, official CI/CD templates (e.g., GitHub Actions), and independent hands-on confirmation of CI pipelines running Unreal successfully.

   • [claimed-docs] “command-line arguments can be an invaluable tool for testing and optimizing your project”
   • [claimed-docs] “Command-line Arguments, also called Additional Launch Parameters, customize how the engine runs on startup.”
   • [claimed-docs] “UnrealEditor.exe <GameName or uproject> -run=cook -targetplatform=<Plat1>+<Plat2>”
   • [claimed-docs] “This command can cook content for a platform, package it up into a platform's native format for distribution, deploys it to the device, and …”
   • [claimed-docs] “Automate time-consuming Asset management tasks in the Unreal Editor, like generating Levels of Detail (LODs) for Static Meshes.”
   • [probe] “PROBE runtime negative (recorded 2026-09-15): Unreal is the least machine-readable presence of the eight — api.github.com/repos/EpicGames/Un…”

   proof ↗⚑ flag

   Bevy—none0/10

   The evidence pack contains no mention of headless mode, CI integration, or automated/scripted execution of Bevy apps; only rendering, ECS, editor-live-reload and general community sentiment are covered. Running headless in CI is a reasonable ask for a game engine, but nothing in the pack demonstrates it.

   ⚑ flag

3. ai-native userConnect an agent via an official MCP server

   weight 3 · round drawn
   Unreal Engine—none0/10

   Unreal Engine is a platform/tool (not itself an agent), so an official MCP server axis applies, but evidence shows no official Epic MCP server exists — a GitHub org search returns 0 results, and the most popular community MCP integration is unmaintained since 2025.

   • [probe] “PROBE runtime negative (recorded 2026-09-15): Unreal is the least machine-readable presence of the eight — api.github.com/repos/EpicGames/Un…”

   proof ↗⚑ flag

   Bevy—none0/10

   Bevy is a game engine/library, not itself an AI agent, so an MCP server axis applies as a fair question, but evidence explicitly shows no official MCP server exists — only nascent third-party tooling (bevy_brp) built on the Bevy Remote Protocol. No official MCP server is documented.

   • [probe] “PROBE runtime negative (recorded 2026-09-15): bevy.org serves no llms.txt (HTTP 404; docs.rs likewise) and no official MCP exists — communit…”
   • [probe] “PROBE llms.txt: HTTP 404 at https://bevy.org/llms.txt”

   proof ↗⚑ flag

4. ai-native userUse an official CLI

   weight 2 · round to Unreal Engine
   Unreal Engine✓fullprobed7/10

   Unreal ships an official CLI surface: UnrealEditor.exe/UAT commands for cooking, packaging, deploying and running projects, plus documented command-line arguments for automation and testing, and Python editor scripting for scriptable workflows — all first-party and independently confirmed as keylessly fetchable per the probe. missing for 10: explicit AI-native framing or agent-oriented tooling around the CLI, and independent hands-on validation of using it in agentic workflows.

   • [claimed-docs] “command-line arguments can be an invaluable tool for testing and optimizing your project”
   • [claimed-docs] “Command-line Arguments, also called Additional Launch Parameters, customize how the engine runs on startup.”
   • [claimed-docs] “UnrealEditor.exe <GameName or uproject> -run=cook -targetplatform=<Plat1>+<Plat2>”
   • [claimed-docs] “This command can cook content for a platform, package it up into a platform's native format for distribution, deploys it to the device, and …”
   • [claimed-docs] “Automate time-consuming Asset management tasks in the Unreal Editor, like generating Levels of Detail (LODs) for Static Meshes.”
   • [probe] “PROBE runtime negative (recorded 2026-09-15): Unreal is the least machine-readable presence of the eight — api.github.com/repos/EpicGames/Un…”

   proof ↗⚑ flag

   Bevy—none0/10

   No evidence of an official Bevy CLI tool anywhere in the evidence pack; only cargo (Rust's generic build tool) and community projects like bevy_brp are mentioned, not a first-party CLI for AI-native workflows.

   ⚑ flag

5. ai-native userDrive the product through a documented public API

   weight 3 · round to Unreal Engine
   Unreal Engine~partialprobed6/10

   Unreal ships genuinely documented public APIs — a Python editor-scripting API for automating asset/editor tasks, a C++ gameplay API, and command-line/UAT automation flags — which a user or script can drive programmatically. However, the probe evidence shows these are not AI-native accessible: no official Epic MCP server, no llms.txt, docs served only as an HTML SPA (no .md fetch), and the GitHub source repo is EULA/account-gated returning 404 to unauthenticated API calls, with the leading community MCP abandoned since April 2025. Missing for 10: AI-agent-discoverable/machine-readable API docs, an official MCP or agent-facing interface, and keyless programmatic access to source/API metadata.

   • [claimed-docs] “Automate time-consuming Asset management tasks in the Unreal Editor, like generating Levels of Detail (LODs) for Static Meshes.”
   • [claimed-docs] “there may be cases where you want precise control over when and how Assets are discovered, loaded, and audited. For these cases, the Asset M…”
   • [claimed-docs] “command-line arguments can be an invaluable tool for testing and optimizing your project”
   • [claimed-docs] “Command-line Arguments, also called Additional Launch Parameters, customize how the engine runs on startup.”
   • [probe] “PROBE runtime negative (recorded 2026-09-15): Unreal is the least machine-readable presence of the eight — api.github.com/repos/EpicGames/Un…”

   proof ↗⚑ flag

   Bevy~partialprobed5/10

   Bevy ships a documented Rust API (in-depth reference docs, docs.rs) and even a first-party 'Bevy Remote Protocol' that a nascent community tool (bevy_brp) uses to drive the engine externally, but there is no AI-oriented public API surface: no llms.txt, no OpenAPI/swagger spec, and no official MCP server, and the remote-protocol tooling is described as nascent/community-only rather than a robust public API for programmatic driving. Missing for 10: an official machine-readable API spec (OpenAPI/llms.txt), first-party remote-control docs beyond community wrappers, and evidence of stable AI-agent usage against the API.

   • [claimed-docs] “Learn how to use Bevy's types, traits and methods using the in-depth reference documentation, complete with inline examples.”
   • [probe] “PROBE llms.txt: HTTP 404 at https://bevy.org/llms.txt”
   • [probe] “PROBE openapi: all candidate paths 404 (https://bevy.org/openapi.json, https://bevy.org/swagger.json, https://bevy.org/api/openapi.json, htt…”
   • [probe] “PROBE runtime negative (recorded 2026-09-15): bevy.org serves no llms.txt (HTTP 404; docs.rs likewise) and no official MCP exists — communit…”

   proof ↗⚑ flag

6. ai-native userBuild against official SDKs

   weight 2 · round to Bevy
   Unreal Engine~partialprobed5/10

   Unreal ships extensive official build surfaces — C++ APIs, Python editor-scripting API, Blueprint visual scripting, plugin SDK, and CLI/automation tooling — all documented on dev.epicgames.com, which functions as an official SDK for building games/tools. However, the probe evidence shows these are poorly suited for AI-native/agentic consumption: no official MCP server exists, GitHub source access is gated (404 without auth), main sites 403 non-browser clients, no llms.txt, and docs aren't served as fetchable markdown, undercutting AI-native usability of the SDK. Missing for 10: official MCP server or agent-friendly API, machine-readable/llms.txt documentation, keyless programmatic access to source and APIs.

   • [claimed-docs] “Creating new Gameplay classes in C++, and all changes will be reflected in the Unreal Editor after compiling with either Visual Studio or XC…”
   • [claimed-docs] “Automate time-consuming Asset management tasks in the Unreal Editor, like generating Levels of Detail (LODs) for Static Meshes.”
   • [claimed-docs] “Plugins are collections of code and data that developers can easily enable or disable within the Editor on a per-project basis.”
   • [claimed-docs] “Access to the source code All platforms & features Forums and documentation on the Epic Developer Community”
   • [probe] “PROBE runtime negative (recorded 2026-09-15): Unreal is the least machine-readable presence of the eight — api.github.com/repos/EpicGames/Un…”

   proof ↗⚑ flag

   Bevy~partialprobed6/10

   Bevy itself ships as an official, versioned Rust SDK (the `bevy` crate on crates.io) with first-party API reference docs, quick-start guides, and migration guides, which is what an AI-native developer would build against (bevy-docs-21, bevy-docs-27, bevy-docs-15, bevy-probe-rt-1). However, pre-1.0 status with breaking changes on nearly every release, community complaints about docs being thin once you leave the intro book, and confirmed absence of llms.txt/AI-consumable doc formats make it harder for AI agents to reliably target the 'official SDK' surface (bevy-probe-rt-1, bevy-comm-12, bevy-comm-14, bevy-probe-1, bevy-probe-rt-2). Missing for 10: llms.txt/AI-friendly doc export, stability guarantees across versions, and independent evidence of AI agents successfully building against the SDK.

   • [claimed-docs] “Bevy is just a normal Rust dependency. You can either add it to an existing Rust project or create a new one.”
   • [claimed-docs] “Learn how to use Bevy's types, traits and methods using the in-depth reference documentation, complete with inline examples.”
   • [claimed-docs] “Every Bevy update brings new functionality and improvements. Follow these guides to migrate your project to the latest Bevy has to offer!”
   • [probe] “PROBE runtime (recorded 2026-09-15): bevy resolves on crates.io — `cargo search bevy` → 'bevy = "0.19.1" # A refreshingly simple data-driven…”
   • [community] “Things have started to stabilize, but unless you're willing to get your hands dirty and deal with regular breaking changes, I don't yet reco…”
   • [community] “I'm put off by the limited docs. I've read the Bevy book, only takes a few minutes, and just like that I'm out of resources to turn to when …”
   • [probe] “PROBE llms.txt: HTTP 404 at https://bevy.org/llms.txt”
   • [probe] “PROBE runtime negative (recorded 2026-09-15): bevy.org serves no llms.txt (HTTP 404; docs.rs likewise) and no official MCP exists — communit…”

   proof ↗⚑ flag

Agentic features

1. ai-native userGet AI-generated insights and suggestions from my data inside the product

   weight 2 · round drawn
   Unreal Engine—none0/10

   No evidence in the pack of Unreal Engine surfacing AI-generated insights or suggestions from project data; docs cover Blueprints, C++, Python scripting, plugins, and networking but nothing about analytics/AI-driven suggestions, and the probe notes the engine has no official MCP or AI-native tooling exposure.

   • [probe] “PROBE runtime negative (recorded 2026-09-15): Unreal is the least machine-readable presence of the eight — api.github.com/repos/EpicGames/Un…”

   proof ↗⚑ flag

   Bevy—none0/10

   The axis applies to this product kind (peer products hold positive or none verdicts on this story), so lack of evidence for an applicable capability is "none", never "na". (na/none harmonized at arena bring-up — see pipeline/scripts/na-harmonize.ts.)

   ⚑ flag

2. ai-native userSet up automations that run autonomously in the background

   weight 2 · round to Unreal Engine
   Unreal Engine~partialprobed5/10

   Unreal exposes Python editor scripting, commandlets, and UAT/command-line automation that can be scripted to run unattended (e.g., asset processing, cooking, packaging) which supports background automation, but nothing in the evidence describes an AI-native agent framework, scheduler, or official API/MCP for autonomous orchestration — and the probe explicitly notes no official Epic MCP and no machine-readable API, undermining AI-native automation setup. missing for 10: official AI-agent/automation orchestration layer, documented scheduling/trigger system for unattended runs, first-party API or MCP for AI agents to invoke automations.

   • [claimed-docs] “Automate time-consuming Asset management tasks in the Unreal Editor, like generating Levels of Detail (LODs) for Static Meshes.”
   • [claimed-docs] “command-line arguments can be an invaluable tool for testing and optimizing your project”
   • [claimed-docs] “Command-line Arguments, also called Additional Launch Parameters, customize how the engine runs on startup.”
   • [claimed-docs] “UnrealEditor.exe <GameName or uproject> -run=cook -targetplatform=<Plat1>+<Plat2>”
   • [claimed-docs] “This command can cook content for a platform, package it up into a platform's native format for distribution, deploys it to the device, and …”
   • [probe] “PROBE runtime negative (recorded 2026-09-15): Unreal is the least machine-readable presence of the eight — api.github.com/repos/EpicGames/Un…”

   proof ↗⚑ flag

   Bevy—none0/10

   The axis applies to this product kind (peer products hold positive or none verdicts on this story), so lack of evidence for an applicable capability is "none", never "na". (na/none harmonized at arena bring-up — see pipeline/scripts/na-harmonize.ts.)

   ⚑ flag

3. ai-native userDelegate tasks to a built-in AI assistant inside the product

   weight 3 · round drawn
   Unreal Engine—none0/10

   No evidence in the pack of any built-in AI assistant inside Unreal Editor that users can delegate tasks to; all documentation covers Blueprints, C++, Python scripting, plugins, and CLI tools, not an AI agent. The probe evidence even notes the lack of any official Epic AI/MCP integration.

   • [probe] “PROBE runtime negative (recorded 2026-09-15): Unreal is the least machine-readable presence of the eight — api.github.com/repos/EpicGames/Un…”
   • [claimed-docs] “Automate time-consuming Asset management tasks in the Unreal Editor, like generating Levels of Detail (LODs) for Static Meshes.”
   • [claimed-docs] “Plugins can add runtime gameplay functionality, modify built-in Engine features (or add new ones), create new file types, and extend the cap…”

   proof ↗⚑ flag

   Bevy—none0/10

   The axis applies to this product kind (peer products hold positive or none verdicts on this story), so lack of evidence for an applicable capability is "none", never "na". (na/none harmonized at arena bring-up — see pipeline/scripts/na-harmonize.ts.)

   ⚑ flag

4. ai-native userOperate the product with natural-language commands

   weight 2 · round drawn
   Unreal Engine—none0/10

   Evidence shows only traditional scripting/programming interfaces (Blueprints, C++, Python, CLI args) with no natural-language command layer; the probe explicitly notes no official Epic MCP server, no llms.txt, and only an unmaintained community MCP project, meaning there's no documented way to operate Unreal via natural-language commands.

   • [probe] “PROBE runtime negative (recorded 2026-09-15): Unreal is the least machine-readable presence of the eight — api.github.com/repos/EpicGames/Un…”
   • [claimed-docs] “Automate time-consuming Asset management tasks in the Unreal Editor, like generating Levels of Detail (LODs) for Static Meshes.”
   • [claimed-docs] “provides the ability for designers to use virtually the full range of concepts and tools generally only available to programmers”

   proof ↗⚑ flag

   Bevy—none0/10

   Bevy is a Rust game engine/library with no evidence of any natural-language command interface; probes confirm no llms.txt, no MCP server, and only nascent third-party remote-protocol tooling (bevy_brp), not a natural-language control layer.

   • [probe] “PROBE llms.txt: HTTP 404 at https://bevy.org/llms.txt”
   • [probe] “PROBE docs-md: HTTP 404 at https://bevy.org/learn/.md”
   • [probe] “PROBE runtime negative (recorded 2026-09-15): bevy.org serves no llms.txt (HTTP 404; docs.rs likewise) and no official MCP exists — communit…”

   proof ↗⚑ flag

Api quality

1. ai-native userExplore an interactive API reference with runnable examples

   weight 2 · round to Bevy
   Unreal Engine—none0/10

   The evidence shows only standard static documentation pages (C++, Blueprints, Python scripting, plugins) with no interactive API reference or runnable/executable code examples; the probe evidence explicitly notes Unreal's docs are not even machine-readable (no llms.txt, .md URLs return HTML shell) and there's no official API sandbox or live-code explorer mentioned anywhere.

   • [probe] “PROBE runtime negative (recorded 2026-09-15): Unreal is the least machine-readable presence of the eight — api.github.com/repos/EpicGames/Un…”
   • [claimed-docs] “Creating new Gameplay classes in C++, and all changes will be reflected in the Unreal Editor after compiling with either Visual Studio or XC…”
   • [claimed-docs] “Automate time-consuming Asset management tasks in the Unreal Editor, like generating Levels of Detail (LODs) for Static Meshes.”

   proof ↗⚑ flag

   Bevy~partialprobed5/10

   Bevy advertises 'in-depth reference documentation, complete with inline examples' and a separate gallery of wasm-compiled examples that run directly in the browser, giving some interactive/runnable exploration of the API surface. But these are two disconnected resources rather than a unified interactive API reference, docs.rs is static/crawlable with no live-run capability, and there's no llms.txt, MCP, or agent-facing interactive console. Missing for 10: a single integrated interactive reference (e.g. rustdoc playground-style 'run' buttons on API docs), agent-facing tooling (llms.txt/MCP) to programmatically explore it, and independent confirmation the wasm examples are tied to the API reference itself.

   • [claimed-docs] “Learn how to use Bevy's types, traits and methods using the in-depth reference documentation, complete with inline examples.”
   • [claimed-docs] “Browse bevy examples compiled to wasm and running directly in your browser!”
   • [probe] “PROBE runtime negative (recorded 2026-09-15): bevy.org serves no llms.txt (HTTP 404; docs.rs likewise) and no official MCP exists — communit…”
   • [probe] “PROBE llms.txt: HTTP 404 at https://bevy.org/llms.txt”

   proof ↗⚑ flag

2. ai-native userDownload a machine-readable API spec (OpenAPI or equivalent)

   weight 2 · round drawn
   Unreal Engine—none0/10

   No evidence of an OpenAPI or similar machine-readable API spec; the probe evidence explicitly finds Unreal's docs and APIs are not machine-readable (no llms.txt, .md docs serve HTML shells, no official MCP/API spec), confirming absence rather than just lack of mention.

   • [probe] “PROBE runtime negative (recorded 2026-09-15): Unreal is the least machine-readable presence of the eight — api.github.com/repos/EpicGames/Un…”

   proof ↗⚑ flag

   Bevy—none0/10

   The axis applies to this product kind (peer products hold positive or none verdicts on this story), so lack of evidence for an applicable capability is "none", never "na". (na/none harmonized at arena bring-up — see pipeline/scripts/na-harmonize.ts.)

   ⚑ flag

3. ai-native userTest against a sandbox environment without touching production data

   weight 1 · round drawn
   Unreal Engine—none0/10

   The axis applies to this product kind (peer products hold positive or none verdicts on this story), so lack of evidence for an applicable capability is "none", never "na". (na/none harmonized at arena bring-up — see pipeline/scripts/na-harmonize.ts.)

   ⚑ flag

   Bevy—none0/10

   The axis applies to this product kind (peer products hold positive or none verdicts on this story), so lack of evidence for an applicable capability is "none", never "na". (na/none harmonized at arena bring-up — see pipeline/scripts/na-harmonize.ts.)

   ⚑ flag

4. ai-native userRely on versioned APIs with a documented deprecation policy

   weight 2 · round to Bevy
   Unreal Engine—none0/10

   No evidence pack item documents API versioning conventions or a deprecation policy for Unreal's C++/Blueprint/Python APIs; the docs cover feature usage (Blueprints, C++, plugins, replication) but never mention deprecation macros, version compatibility guarantees, or a documented sunset policy. The probe evidence further shows Unreal's docs/API surface is poorly machine-readable, with no llms.txt or markdown API references that would expose such a policy.

   • [probe] “PROBE runtime negative (recorded 2026-09-15): Unreal is the least machine-readable presence of the eight — api.github.com/repos/EpicGames/Un…”

   proof ↗⚑ flag

   Bevy!disputedcontradicted3/10

   Bevy publishes migration guides for each release (bevy-docs-15) implying some versioning discipline, but there is no documented deprecation policy, and hands-on evidence shows the API is pre-1.0 with frequent breaking changes each release requiring real rework (bevy-comm-12, bevy-comm-13, bevy-probe-rt-1), directly undercutting reliability for an AI agent trained on prior APIs. Missing for 10: an explicit deprecation/versioning policy document, semver guarantees, and evidence that breaking changes are flagged/deprecated before removal rather than silently changed.

   • [claimed-docs] “Every Bevy update brings new functionality and improvements. Follow these guides to migrate your project to the latest Bevy has to offer!”
   • [community] “Things have started to stabilize, but unless you're willing to get your hands dirty and deal with regular breaking changes, I don't yet reco…”
   • [community] “On the last update 0.10 -> 0.11, I had to make quite a few changes on my app, but this time it compiled out of the box!”
   • [probe] “PROBE runtime (recorded 2026-09-15): bevy resolves on crates.io — `cargo search bevy` → 'bevy = "0.19.1" # A refreshingly simple data-driven…”

   proof ↗⚑ flag

Agent editor

1. ai-native userAn agent can drive the editor and project programmatically — create scenes and nodes, edit properties, trigger builds — through a documented scriptable interface

   weight 3 · round to Unreal Engine
   Unreal Engine~partialprobed6/10

   Unreal documents a genuine scriptable interface — the Python Editor Scripting API for asset/property automation (docs-4, docs-12), Blueprints for visual node-based logic (docs-1), and CLI/UAT commands for cooking, packaging and triggering builds (docs-7,14,16,17) — which together let a script or agent create/edit content and trigger builds. However, the probe evidence shows no official Epic MCP server or AI-agent-oriented interface exists (0 results for org:EpicGames MCP repos), the most popular community MCP wrapper is unmaintained since 2025, and the docs themselves are not agent-friendly (SPA HTML, no llms.txt, .md suffix doesn't return markdown), undermining ease of programmatic/agentic access despite the underlying scripting capability being real. Missing for 10: official AI-agent/MCP integration, machine-readable documentation, evidence of an agent actually driving these interfaces end-to-end.

   • [claimed-docs] “Automate time-consuming Asset management tasks in the Unreal Editor, like generating Levels of Detail (LODs) for Static Meshes.”
   • [claimed-docs] “there may be cases where you want precise control over when and how Assets are discovered, loaded, and audited. For these cases, the Asset M…”
   • [claimed-docs] “provides the ability for designers to use virtually the full range of concepts and tools generally only available to programmers”
   • [claimed-docs] “command-line arguments can be an invaluable tool for testing and optimizing your project”
   • [claimed-docs] “UnrealEditor.exe <GameName or uproject> -run=cook -targetplatform=<Plat1>+<Plat2>”
   • [claimed-docs] “This command can cook content for a platform, package it up into a platform's native format for distribution, deploys it to the device, and …”
   • [probe] “PROBE runtime negative (recorded 2026-09-15): Unreal is the least machine-readable presence of the eight — api.github.com/repos/EpicGames/Un…”

   proof ↗⚑ flag

   Bevy~partialprobed3/10

   Bevy has a first-party Bevy Remote Protocol that could support programmatic scene/entity manipulation, and a community tool (bevy_brp) built on it, but there is no official documentation, no llms.txt, and no official MCP server — the community tooling itself is described as nascent (70 stars). Since Bevy is a code-first Rust crate, most 'scripting' is done by writing/recompiling Rust code rather than through a documented runtime scriptable interface for driving an editor. Missing for 10: first-party documented API/schema for the Remote Protocol, official MCP or agent-facing tooling, evidence of hands-on agent use creating scenes/nodes and triggering builds via that interface.

   • [probe] “PROBE runtime negative (recorded 2026-09-15): bevy.org serves no llms.txt (HTTP 404; docs.rs likewise) and no official MCP exists — communit…”
   • [probe] “PROBE llms.txt: HTTP 404 at https://bevy.org/llms.txt”
   • [claimed-docs] “Create, save, and load ECS worlds using Bevy's Scene system”

   proof ↗⚑ flag

Codegen

1. ai-native userLLM-generated code mostly works on the first try — stable, well-documented APIs with abundant public examples the models have seen

   weight 2 · round to Bevy
   Unreal Engine—none0/10

   No evidence directly addresses whether LLM-generated Unreal C++/Blueprint code works reliably on first try; the pack only shows general API docs exist and community comments about C++ complexity and blueprint limitations. The probe evidence even indicates docs are poorly machine-readable (403s, no llms.txt, gated source) which undercuts the 'abundant examples models have seen' premise but isn't a direct test of code-gen success either.

   • [claimed-docs] “Creating new Gameplay classes in C++, and all changes will be reflected in the Unreal Editor after compiling with either Visual Studio or XC…”
   • [community] “My main problem with UE is C++, I don't want to even try to download files or read json in a blueprint.”
   • [community] “blueprints are great for prototyping, but once you have too much complexity in a BP it can easily cascade inefficiencies to the point it bec…”
   • [probe] “PROBE runtime negative (recorded 2026-09-15): Unreal is the least machine-readable presence of the eight — api.github.com/repos/EpicGames/Un…”

   proof ↗⚑ flag

   Bevy!disputedcontradicted4/10

   Bevy has abundant examples and reference docs (bevy-docs-16, bevy-docs-22, bevy-docs-27) which help LLM familiarity, but concrete community evidence shows the API is unstable pre-1.0 with breaking changes almost every release, requiring real migration work each time (bevy-comm-12, bevy-comm-13, bevy-probe-rt-1) — meaning LLMs trained on older versions likely generate code that fails to compile against current APIs. Docs are also reported as thin/outdated relative to the pace of change (bevy-comm-14, bevy-comm-15), and there's no llms.txt or first-party AI-consumption docs (bevy-probe-1, bevy-probe-rt-2). missing for 10: evidence of first-try success rate for LLM-generated Bevy code, stable API surface across versions, and first-party AI-friendly documentation.

   • [community] “Things have started to stabilize, but unless you're willing to get your hands dirty and deal with regular breaking changes, I don't yet reco…”
   • [community] “On the last update 0.10 -> 0.11, I had to make quite a few changes on my app, but this time it compiled out of the box!”
   • [community] “I'm put off by the limited docs. I've read the Bevy book, only takes a few minutes, and just like that I'm out of resources to turn to when …”
   • [community] “There's an unofficial complement to the docs... Unfortunately it's somewhat out of date... The effort to keep it up to date is somewhat low …”
   • [probe] “PROBE runtime (recorded 2026-09-15): bevy resolves on crates.io — `cargo search bevy` → 'bevy = "0.19.1" # A refreshingly simple data-driven…”
   • [probe] “PROBE runtime negative (recorded 2026-09-15): bevy.org serves no llms.txt (HTTP 404; docs.rs likewise) and no official MCP exists — communit…”
   • [claimed-docs] “Examples that show how to use the various features of Bevy.”

   proof ↗⚑ flag

Copilot

1. ai-native userAn official AI assistant inside the engine helps with engine tasks — generating scripts, answering API questions, scaffolding scenes or assets

   weight 2 · round drawn
   Unreal Engine—none0/10

   No evidence of an official in-engine AI assistant for generating scripts, answering API questions, or scaffolding scenes; the pack only covers Blueprints, C++, Python editor scripting, and plugins as manual tooling. The probe evidence explicitly notes no official Epic MCP/AI integration and that the most popular community MCP project is unmaintained.

   • [probe] “PROBE runtime negative (recorded 2026-09-15): Unreal is the least machine-readable presence of the eight — api.github.com/repos/EpicGames/Un…”
   • [claimed-docs] “Automate time-consuming Asset management tasks in the Unreal Editor, like generating Levels of Detail (LODs) for Static Meshes.”

   proof ↗⚑ flag

   Bevy—none0/10

   Bevy is a Rust game engine/library with no evidence of an official in-engine AI assistant; probes confirm no llms.txt, no official MCP, and only nascent third-party tooling (bevy_brp).

   • [probe] “PROBE llms.txt: HTTP 404 at https://bevy.org/llms.txt”
   • [probe] “PROBE runtime negative (recorded 2026-09-15): bevy.org serves no llms.txt (HTTP 404; docs.rs likewise) and no official MCP exists — communit…”

   proof ↗⚑ flag

Formats

1. technical artistStandard interchange formats — glTF, FBX, USD — import cleanly

   weight 2 · round drawn
   Unreal Engine—none0/10

   The evidence pack contains no documentation, community, or probe citations addressing glTF, FBX, or USD import functionality in Unreal Engine; all provided docs cover Blueprints, C++, plugins, networking, and licensing instead. Since asset-pipeline import is a fair and applicable axis for a game engine, but no supporting evidence exists in this pack, the verdict is none.

   ⚑ flag

   Bevy—none0/10

   No evidence anywhere in the pack mentions glTF, FBX, USD, or any interchange-format import/asset-pipeline support; only glTF is a commonly known Bevy asset format but it's not cited here. Missing for 10: any docs or community mention of glTF/FBX/USD import, format fidelity, or asset-pipeline tooling.

   ⚑ flag

Import

1. technical artistAsset import is automatable — import hooks, presets, and pipeline scripts process incoming assets without hand-clicking each one

   weight 2 · round to Unreal Engine
   Unreal Engine~partialclaimed6/10

   Docs confirm Python scripting can automate asset-management tasks like LOD generation, and the Asset Manager gives programmatic control over asset discovery/loading, while Plugins can add new file-type handling — together these support scripted, non-interactive asset pipelines. However, there's no explicit documentation of dedicated 'import hooks' (e.g. post-import delegates/factories) or preset-based automated import workflows, and no independent/community confirmation that artists actually use this for hands-off batch import. missing for 10: explicit import-hook/factory API docs, named import-preset tooling, and third-party/community validation of automated import pipelines.

   • [claimed-docs] “Automate time-consuming Asset management tasks in the Unreal Editor, like generating Levels of Detail (LODs) for Static Meshes.”
   • [claimed-docs] “provides a framework for managing Assets that can divide content into chunks that make sense in the context of your project”
   • [claimed-docs] “there may be cases where you want precise control over when and how Assets are discovered, loaded, and audited. For these cases, the Asset M…”
   • [claimed-docs] “Plugins can add runtime gameplay functionality, modify built-in Engine features (or add new ones), create new file types, and extend the cap…”
   • [claimed-docs] “Plugins are collections of code and data that developers can easily enable or disable within the Editor on a per-project basis.”

   proof ↗⚑ flag

   Bevy~partialcommunity3/10

   Bevy's Asset V2 system does support preprocessing and .meta files, which one community commenter calls 'super useful' for pipeline automation, but no first-party docs describe import hooks, presets, or scripting workflows for batch/automated asset processing. missing for 10: official documentation on asset import hooks/presets, evidence of scripted/batch pipeline tooling, and independent confirmation beyond a single community mention.

   • [community] “Bevy is one of my favorite game engines, especially for larger projects. Asset V2 preprocessing and .meta files look super useful.”

   proof ↗⚑ flag

Marketplace

1. game developerA large asset store or package ecosystem gives me ready-made models, tools, and plugins

   weight 2 · round drawn
   Unreal Engine~partialprobed5/10

   Docs show a genuine plugin and asset-management ecosystem (plugins can add gameplay features, new file types, editor extensions; Asset Manager for content organization) and community comment notes strong third-party program/community support, but there is no direct evidence in the pack describing the actual Marketplace/Fab asset store, its catalog size, or the quality of ready-made models — the probe entry only notes fab.com exists but is API-gated, not its content richness. Missing for 10: concrete marketplace/store catalog evidence, examples of ready-made models/tools available, and independent user reviews of the store experience.

   • [claimed-docs] “Plugins can add runtime gameplay functionality, modify built-in Engine features (or add new ones), create new file types, and extend the cap…”
   • [claimed-docs] “Plugins are collections of code and data that developers can easily enable or disable within the Editor on a per-project basis.”
   • [claimed-docs] “provides a framework for managing Assets that can divide content into chunks that make sense in the context of your project”
   • [claimed-docs] “there may be cases where you want precise control over when and how Assets are discovered, loaded, and audited. For these cases, the Asset M…”
   • [community] “Unreal was already the best engine purely on being easy to work with, support from third party programs and community, none of those things …”
   • [probe] “PROBE runtime negative (recorded 2026-09-15): Unreal is the least machine-readable presence of the eight — api.github.com/repos/EpicGames/Un…”

   proof ↗⚑ flag

   Bevy~partialcommunity5/10

   Bevy explicitly maintains an official third-party 'Assets' page listing community plugins, tools, and learning resources (bevy-docs-17), and community comments confirm an active ecosystem contributing new features and crates (bevy-comm-19). However, this is a curated links page rather than an integrated in-engine asset store, and the ecosystem is described as young/fragmented with docs gaps and frequent breaking changes affecting third-party plugin compatibility (bevy-comm-12, bevy-comm-15). Missing for 10: evidence of a large volume/maturity of ready-made models or marketplace-scale assets, integrated store UI, and quantified ecosystem size or quality assurance for third-party plugins.

   • [claimed-docs] “A collection of third-party Bevy assets, plugins, learning resources, and apps made by the community.”
   • [community] “Something delightful about this update: it has a lot of new features, some very early, but all by different authors. Seems like such a commu…”
   • [community] “Things have started to stabilize, but unless you're willing to get your hands dirty and deal with regular breaking changes, I don't yet reco…”
   • [community] “There's an unofficial complement to the docs... Unfortunately it's somewhat out of date... The effort to keep it up to date is somewhat low …”

   proof ↗⚑ flag

1. ai-native userPerform bulk operations across many items at once

   weight 2 · round to Unreal Engine
   Unreal Engine~partialprobed5/10

   Unreal's Python editor-scripting API and Asset Manager are documented to automate time-consuming asset tasks (e.g., batch-generating LODs for Static Meshes) and manage large sets of Assets in chunks, which supports bulk operations across many items, and UAT/command-line tooling and cooking commands support batch build/deploy across multiple platforms/targets. However there is no concrete first-party example of an AI-native agent performing bulk edits, no official MCP server, and the probe evidence flags Unreal as the least machine-readable/agent-accessible of comparable products (gated APIs, 403s, no llms.txt), undercutting AI-native automation-depth claims. Missing for 10: worked examples of bulk operations orchestrated end-to-end, official AI/agent tooling or MCP integration, independent hands-on confirmation of scripted bulk workflows.

   • [claimed-docs] “Automate time-consuming Asset management tasks in the Unreal Editor, like generating Levels of Detail (LODs) for Static Meshes.”
   • [claimed-docs] “provides a framework for managing Assets that can divide content into chunks that make sense in the context of your project”
   • [claimed-docs] “there may be cases where you want precise control over when and how Assets are discovered, loaded, and audited. For these cases, the Asset M…”
   • [claimed-docs] “UnrealEditor.exe <GameName or uproject> -run=cook -targetplatform=<Plat1>+<Plat2>”
   • [claimed-docs] “This command can cook content for a platform, package it up into a platform's native format for distribution, deploys it to the device, and …”
   • [probe] “PROBE runtime negative (recorded 2026-09-15): Unreal is the least machine-readable presence of the eight — api.github.com/repos/EpicGames/Un…”

   proof ↗⚑ flag

   Bevy—none0/10

   The axis applies to this product kind (peer products hold positive or none verdicts on this story), so lack of evidence for an applicable capability is "none", never "na". (na/none harmonized at arena bring-up — see pipeline/scripts/na-harmonize.ts.)

   ⚑ flag

2. ai-native userDefine rules that trigger actions automatically on events

   weight 3 · round to Unreal Engine
   Unreal Engine✓fullcommunity6/10

   Unreal's Blueprint visual scripting and C++ delegate system explicitly support binding functions to be invoked automatically at a future time/event (dynamic delegates), and Blueprints expose event graphs for designers to wire up event-triggered logic without code. Community commentary confirms Blueprints are used for prototyping event-driven logic though complexity pushes users to C++. Missing for 10: explicit documentation of Event Dispatchers/Event Graph event-binding UI, and independent hands-on validation of rule-trigger reliability at scale.

   • [claimed-docs] “provides the ability for designers to use virtually the full range of concepts and tools generally only available to programmers”
   • [claimed-docs] “You can dynamically bind a delegate to a member function of an arbitrary object, calling the function on the object at a future time”
   • [community] “blueprints are great for prototyping, but once you have too much complexity in a BP it can easily cascade inefficiencies to the point it bec…”

   proof ↗⚑ flag

   Bevy—none0/10

   The evidence pack describes Bevy's ECS, rendering, audio, and UI features but never mentions an event/trigger/rule system (e.g., Bevy Events, Observers, or ECS hooks) that would let a user define rules firing automatically on events. While such automation is plausible for a game engine's ECS, no evidence in the pack substantiates it.

   ⚑ flag

3. ai-native userVersion, review, and roll back my automations

   weight 1 · round drawn
   Unreal Engine—none0/10

   The evidence pack covers Blueprints, C++, Python scripting, plugins, asset management, and cooking, but contains no mention of version control integration, change review/diffing, or rollback mechanisms for Blueprints, Python scripts, or other automations. This is a plausible axis for a dev engine (e.g., source control on Blueprints), but no supporting evidence exists.

   ⚑ flag

   Bevy—none0/10

   The axis applies to this product kind (peer products hold positive or none verdicts on this story), so lack of evidence for an applicable capability is "none", never "na". (na/none harmonized at arena bring-up — see pipeline/scripts/na-harmonize.ts.)

   ⚑ flag

2d

1. game developer2D is a first-class workflow — sprites, tilemaps, 2D physics — not a 3D afterthought

   weight 2 · round to Bevy
   Unreal Engine—none0/10

   The evidence pack contains no mention of sprites, tilemaps, Paper2D, or 2D physics support in Unreal Engine—only C++, Blueprints, plugins, networking, and licensing topics. Since a 3D-first engine could plausibly ship a first-class 2D workflow, this axis applies, but no evidence documents it, so the story is unsupported.

   ⚑ flag

   Bevy~partialclaimed5/10

   Bevy's official docs explicitly list 2D rendering as a first-class feature alongside 3D (bevy-docs-2, bevy-docs-3), suggesting parity rather than a 3D-only focus, and community feedback confirms active engine use for real projects. However, there is no evidence in the pack of built-in tilemap support or first-party 2D physics (these are known to be third-party crates in the Bevy ecosystem), so the story's specific claims about tilemaps and 2D physics being first-class are unconfirmed. Missing for 10: evidence of native/first-party tilemap support, evidence of native/first-party 2D physics integration, and any community confirmation of 2D-specific workflow maturity.

   • [claimed-docs] “Render real-time 2D graphics for games and apps”
   • [claimed-docs] “A modern and flexible 3D renderer”
   • [claimed-docs] “Extensible: custom shaders, materials, and render pipelines”

   proof ↗⚑ flag

Performance

1. game developerProfile and scale — a real profiler, plus data-oriented paths (ECS, jobs, instancing) when scenes get heavy

   weight 2 · round to Bevy
   Unreal Engine—none0/10

   The evidence pack contains no documentation or community evidence about Unreal Insights, stat/profiling commands, GPU profiling, or data-oriented paths like Mass Entity/ECS, job systems, or GPU instancing — only generic command-line-argument docs mentioning 'testing and optimizing' in passing. Profiling and data-oriented scaling are core, expected capabilities for a AAA game engine, so the axis applies, but nothing in the pack demonstrates a real profiler or ECS/jobs/instancing systems.

   • [claimed-docs] “command-line arguments can be an invaluable tool for testing and optimizing your project”
   • [claimed-docs] “Command-line Arguments, also called Additional Launch Parameters, customize how the engine runs on startup.”

   proof ↗⚑ flag

   Bevy~partialcommunity4/10

   Bevy's data-oriented ECS is well documented as the foundation for all engine/game logic (bevy-docs-1, bevy-docs-14, bevy-docs-20), and community accounts corroborate its data-driven, ECS-first workflow (bevy-comm-17). However, the evidence pack contains no mention of a built-in profiler/diagnostics tool, explicit job/parallel-system scheduling, or GPU instancing for heavy scenes — core parts of the story. Missing for 10: dedicated profiler tooling (e.g. tracing/diagnostics plugin), explicit job-system/parallelism documentation, and instancing support evidence.

   • [claimed-docs] “All engine and game logic uses Bevy ECS, a custom Entity Component System”
   • [claimed-docs] “Components: Rust structs that implement the Component trait”
   • [claimed-docs] “Unlike other Rust ECS implementations, which often require complex lifetimes, traits, builder patterns, or macros, Bevy ECS uses normal Rust…”
   • [community] “Pros: Very nice to work in Rust engine + Rust game. Once you get your brain thinking ECS it's tough to go back, feels very flexible. Very li…”

   proof ↗⚑ flag

Physics

1. game developerBuilt-in physics — rigid bodies, collisions, raycasts — works out of the box

   weight 2 · round drawn
   Unreal Engine—none0/10

   The evidence pack contains no documentation, community reports, or probes specifically addressing Unreal's physics system (rigid bodies, collision detection, raycasting, Chaos/PhysX). Coverage is entirely about Blueprints, C++, plugins, asset management, networking, licensing, and community sentiment on cost/usability — none of which substantiates the built-in physics story.

   ⚑ flag

   Bevy—none0/10

   The evidence pack covers ECS, rendering, audio, UI, and scenes but contains no mention of physics, rigid bodies, collision detection, or raycasting capabilities. Built-in physics is a fair question for a game engine's core-engine axis, but nothing in the docs or community evidence shows Bevy ships this out of the box.

   ⚑ flag

Rendering

1. game developerThe engine ships a modern production 3D renderer — PBR materials, global illumination or baked lighting, shadows, post-processing

   weight 3 · round drawn
   Unreal Engine~partialcommunity5/10

   Community evidence confirms Unreal's renderer includes Lumen for real-time global illumination/reflections and general praise for lighting quality, supporting the GI/rendering claim, but the evidence pack lacks first-party documentation or hands-on confirmation of PBR material workflows, shadow systems, or the post-processing pipeline explicitly. missing for 10: explicit docs/evidence on PBR material editor, shadow mapping/ray-traced shadows, and post-process volume/effects stack.

   • [community] “Lumen implements efficient Software Ray Tracing, allowing for global illumination and reflections to run on a wide range of video cards, whi…”
   • [community] “For someone who's actually using UE4 as an artistic break for web dev, I thoroughly recommend it. It allows you to create great environments…”

   proof ↗⚑ flag

   Bevy~partialcommunity5/10

   Docs confirm a 'modern and flexible 3D renderer' with extensible custom shaders/materials/pipelines, and community hands-on feedback confirms shadows exist (though called 'jagged/low-res, reminds me of early Unity shadows'). However, the evidence pack never mentions global illumination, baked lighting, or a post-processing stack explicitly. Missing for 10: explicit documentation of GI/baked lighting support, explicit post-processing feature list, and independent corroboration of PBR material quality beyond the shadow-quality caveat.

   • [claimed-docs] “A modern and flexible 3D renderer”
   • [claimed-docs] “Extensible: custom shaders, materials, and render pipelines”
   • [community] “Not a criticism, but model projected shadows are very jagged or really low-res, reminds me of early Unity shadows.”

   proof ↗⚑ flag

Collaboration

1. studio leadThe project format and tooling play well with version control and multi-person teams — mergeable scenes, diffable text formats, or built-in collaboration

   weight 2 · round drawn
   Unreal Engine—none0/10

   The evidence pack contains no mention of Unreal's scene/level file formats, diffability, source-control integration (e.g., Perforce/Git-LFS workflows), or any built-in multi-user collaboration tooling; it only covers Blueprints, C++, plugins, networking replication, and licensing. Missing for 10: any documentation or community evidence on .uasset/.umap format mergeability, text-based diffable formats, or built-in collaboration features like Multi-User Editing.

   ⚑ flag

   Bevy—none0/10

   Evidence mentions a Scene system for saving/loading ECS worlds (bevy-docs-8) but nothing about its text format being diffable/mergeable, nor any built-in multi-user collaboration tooling. The 'code-first' workflow noted in bevy-probe-rt-2 is framed around agent-driven development, not team version-control workflows, so it doesn't substantiate this story.

   • [claimed-docs] “Create, save, and load ECS worlds using Bevy's Scene system”
   • [probe] “PROBE runtime negative (recorded 2026-09-15): bevy.org serves no llms.txt (HTTP 404; docs.rs likewise) and no official MCP exists — communit…”

   proof ↗⚑ flag

Editor

1. technical artistA full visual editor — viewport, inspector, prefabs/scene composition — is the primary way to build levels

   weight 3 · round to Unreal Engine
   Unreal Engine✓fullcommunity7/10

   Unreal's editor-centric workflow (Blueprints visual scripting, Editor extensions, Asset Manager, Level building/testing via UE Toolbar) is well documented as the primary way to construct levels and gameplay without programmer-only tools, and community comments (comm-3, comm-11, comm-16) corroborate that it's an actual GUI-driven editor experience artists use. missing for 10: explicit documentation naming 'viewport' and 'inspector' panels, and 'prefab' terminology (Unreal uses Blueprint/Actor classes instead) with independent hands-on confirmation of scene-composition workflow specifically for technical artists.

   • [claimed-docs] “provides the ability for designers to use virtually the full range of concepts and tools generally only available to programmers”
   • [claimed-docs] “Plugins can add runtime gameplay functionality, modify built-in Engine features (or add new ones), create new file types, and extend the cap…”
   • [claimed-docs] “provides a framework for managing Assets that can divide content into chunks that make sense in the context of your project”
   • [claimed-docs] “Use UE Toolbar to quickly test a part of your currently loaded Level for testing and debugging.”
   • [community] “Unreal was already the best engine purely on being easy to work with, support from third party programs and community, none of those things …”
   • [community] “What I hate about unity is the whole interface editor thing... Is this Unreal Engine more earth to earth when it comes to programming?”

   proof ↗⚑ flag

   Bevy—none0/10

   Bevy's evidence describes a code-first Rust ECS engine (components, systems, scenes-as-data, hot reloading) but nothing about a visual editor with viewport, inspector, or prefab/scene composition UI; comment bevy-comm-8 even suggests users hope NOT to be forced into an in-engine editor, and probes show no official tooling filling this gap. Missing for full/partial credit: any first-party viewport/inspector GUI, prefab authoring workflow, or scene-composition editor.

   • [claimed-docs] “Create, save, and load ECS worlds using Bevy's Scene system”
   • [claimed-docs] “Get instant feedback on your changes without app restarts or recompiles”
   • [community] “The integrated code editor in Godot is actually something I don't like... I hope that Bevy users won't be forced to use the Bevy editor for …”

   proof ↗⚑ flag

Extensibility

1. game developerExtend and automate the editor itself — custom tools, editor scripts, plugins that manipulate scenes and assets programmatically

   weight 3 · round to Unreal Engine
   Unreal Engine✓fullcommunity8/10

   Docs confirm multiple official extension paths: Python editor scripting for automating asset/editor tasks, Blueprints for designer-level scripting, C++ for deep gameplay/editor class extension, and a Plugins system explicitly designed to 'extend the capabilities of the Editor.' These are core, well-documented first-party mechanisms for programmatic scene/asset manipulation and editor customization. Missing for 10: independent hands-on corroboration specifically of the Python/editor-scripting API (community evidence mostly discusses C++/Blueprint complexity rather than editor automation), and no mention of newer scripting surfaces like the Editor Utility Widgets or Python API depth in third-party sources.

   • [claimed-docs] “Automate time-consuming Asset management tasks in the Unreal Editor, like generating Levels of Detail (LODs) for Static Meshes.”
   • [claimed-docs] “Plugins can add runtime gameplay functionality, modify built-in Engine features (or add new ones), create new file types, and extend the cap…”
   • [claimed-docs] “Plugins are collections of code and data that developers can easily enable or disable within the Editor on a per-project basis.”
   • [claimed-docs] “provides the ability for designers to use virtually the full range of concepts and tools generally only available to programmers”
   • [claimed-docs] “Creating new Gameplay classes in C++, and all changes will be reflected in the Unreal Editor after compiling with either Visual Studio or XC…”
   • [community] “blueprints are great for prototyping, but once you have too much complexity in a BP it can easily cascade inefficiencies to the point it bec…”

   proof ↗⚑ flag

   Bevy—none0/10

   Bevy's evidence shows only a code-first workflow (ECS, scenes, plugins) and mentions no official editor application to extend; the closest hint is a third-party 'bevy_brp' remote-protocol tool with just 70 stars, not first-party editor scripting/plugin support for manipulating scenes and assets. missing for 10: any first-party editor product, documented editor scripting/plugin API, or mature ecosystem tooling for automating scene/asset manipulation via an editor UI.

   • [probe] “PROBE runtime negative (recorded 2026-09-15): bevy.org serves no llms.txt (HTTP 404; docs.rs likewise) and no official MCP exists — communit…”
   • [claimed-docs] “Create, save, and load ECS worlds using Bevy's Scene system”

   proof ↗⚑ flag

Ci

1. game developerBuild and export the project from the command line, headless, in CI — no human clicking an editor

   weight 3 · round to Unreal Engine
   Unreal Engine✓fullprobed8/10

   Official docs give concrete CLI commands for headless building/cooking/packaging/deploying a project (UnrealEditor.exe -run=cook, and the build/cook/package/deploy/run automation command), plus a dedicated command-line-arguments reference for scripted/CI use, all without needing to open the editor UI. Missing for 10: independent third-party CI pipeline case study confirming it works end-to-end, and explicit mention of UAT/BuildCookRun tool name or exit-code/scripting integration details.

   • [claimed-docs] “UnrealEditor.exe <GameName or uproject> -run=cook -targetplatform=<Plat1>+<Plat2>”
   • [claimed-docs] “This command can cook content for a platform, package it up into a platform's native format for distribution, deploys it to the device, and …”
   • [claimed-docs] “Command-line Arguments, also called Additional Launch Parameters, customize how the engine runs on startup.”
   • [claimed-docs] “command-line arguments can be an invaluable tool for testing and optimizing your project”
   • [probe] “PROBE runtime negative (recorded 2026-09-15): Unreal is the least machine-readable presence of the eight — api.github.com/repos/EpicGames/Un…”

   proof ↗⚑ flag

   Bevy~partialprobed5/10

   Bevy is a code-first Rust library built and run via cargo, with no mandatory editor (bevy-docs-21, bevy-comm-8, bevy-probe-rt-2), which inherently supports command-line/CI builds. However, there is no explicit documentation of a headless mode flag, export pipeline, or CI-specific tooling/examples, and no official CI templates or GitHub Actions references are present in the evidence pack. missing for 10: explicit headless-mode/export documentation, CI pipeline examples or templates, and confirmation of asset-building/export automation without a GUI step.

   • [claimed-docs] “Bevy is just a normal Rust dependency. You can either add it to an existing Rust project or create a new one.”
   • [community] “The integrated code editor in Godot is actually something I don't like... I hope that Bevy users won't be forced to use the Bevy editor for …”
   • [probe] “PROBE runtime negative (recorded 2026-09-15): bevy.org serves no llms.txt (HTTP 404; docs.rs likewise) and no official MCP exists — communit…”
   • [probe] “PROBE runtime (recorded 2026-09-15): bevy resolves on crates.io — `cargo search bevy` → 'bevy = "0.19.1" # A refreshingly simple data-driven…”

   proof ↗⚑ flag

Server

1. game developerGame logic runs headless on servers — a dedicated-server or server-runtime build without rendering

   weight 2 · round drawn
   Unreal Engine—none0/10

   The evidence pack covers general networking/replication (client-server sync), command-line arguments, and cooking/packaging, but nowhere mentions Unreal's dedicated-server build target, a headless/no-rendering server runtime, or how to produce a server-only executable. Without explicit documentation of a server-only build path, this axis is unsupported by the given evidence. Missing for 10: any mention of a 'Server' build target, -server or -nullrhi headless launch flags, or dedicated-server packaging instructions.

   • [claimed-docs] “Replication is the name for the process of synchronizing data and procedure calls between clients and servers”
   • [claimed-docs] “Replication is the name for the process of synchronizing data and procedure calls between clients and servers.”
   • [claimed-docs] “UnrealEditor.exe <GameName or uproject> -run=cook -targetplatform=<Plat1>+<Plat2>”
   • [claimed-docs] “This command can cook content for a platform, package it up into a platform's native format for distribution, deploys it to the device, and …”
   • [claimed-docs] “Command-line Arguments, also called Additional Launch Parameters, customize how the engine runs on startup.”

   proof ↗⚑ flag

   Bevy—none0/10

   The evidence pack covers Bevy's ECS, rendering, UI, audio, and platform support, but contains no mention of a headless/dedicated-server build mode, disabling rendering plugins, or server-runtime configuration. Since this is a plausible and common need for a game engine, absence of evidence means the axis is unmet rather than inapplicable.

   ⚑ flag

Testing

1. game developerTests run headlessly — unit and integration tests of game code execute in CI against the real engine

   weight 2 · round drawn
   Unreal Engine—none0/10

   The evidence pack only shows generic command-line argument docs and a UE Toolbar mention for ad-hoc level testing/debugging; there is no evidence of Unreal's Automation System, Gauntlet, or any documented headless unit/integration test execution flow running the real engine in CI. Missing for 10: mention of the Automation Testing framework, -nullrhi/-unattended/-ExecCmds test invocation, CI integration examples, or independent reports of headless test runs against the real engine.

   ⚑ flag

   Bevy—none0/10

   The evidence pack contains no mention of headless mode, CI test execution, integration testing, or automated test frameworks for Bevy game logic — nothing about running engine/game tests without a display or in continuous integration.

   ⚑ flag

Governance

1. studio leadThe project's governance and funding are transparent — a foundation, published finances, or a public roadmap I can plan against

   weight 1 · round drawn
   Unreal Engine—none0/10

   Evidence covers licensing costs, royalty terms, and technical documentation, but nothing indicates a governing foundation, published financial statements, or a public roadmap for Unreal Engine — Epic Games remains a private, closed-governance company with only EULA/royalty terms disclosed (unreal-docs-10, unreal-comm-9, unreal-comm-13).

   • [claimed-docs] “Access to the source code”
   • [community] “For those who don't know what the deal is with Unreal Engine, there's no charge until you get the first million dollars in revenue. Then the…”
   • [community] “It appears they've backed off on the royalties, too: originally, it was 5% of gross, and now it's 5% of gross after $3000 sales per quarter.”

   proof ↗⚑ flag

   Bevy—none0/10

   Evidence documents Bevy's open-source MIT/Apache-2.0 licensing and community activity, but nothing about a governing foundation, published finances, or an official public roadmap a studio could plan against — only migration guides for past releases are mentioned. missing for 10: evidence of a foundation or legal entity, published budget/financials, and a forward-looking public roadmap.

   • [claimed-docs] “It is free and open-source forever under your choice of the MIT or Apache 2.0 licenses.”
   • [claimed-docs] “100% free. Forever and always * Open Source under the permissive MIT or Apache 2.0 licenses * No contracts * No license fees * No sa…”
   • [claimed-docs] “Every Bevy update brings new functionality and improvements. Follow these guides to migrate your project to the latest Bevy has to offer!”
   • [community] “Something delightful about this update: it has a lot of new features, some very early, but all by different authors. Seems like such a commu…”

   proof ↗⚑ flag

License

1. studio leadThe license is permissive with no royalties or per-install fees — I keep what my game earns

   weight 3 · round to Bevy
   Unreal Engine—none0/10

   Community evidence explicitly documents that Unreal charges a 5% royalty on gross revenue after the first $1M (or $3,000/quarter) — this is the opposite of 'no royalties, keep what you earn.' No evidence pack item supports a royalty-free/no-fee licensing model; instead multiple citations (comm-1, comm-9, comm-13, comm-2) confirm a royalty-based commercial license.

   • [community] “UE offers everything free... Only way to pay to use Unreal Engine is to earn more than $1,000,000 USD which for most people means everything…”
   • [community] “For those who don't know what the deal is with Unreal Engine, there's no charge until you get the first million dollars in revenue. Then the…”
   • [community] “It appears they've backed off on the royalties, too: originally, it was 5% of gross, and now it's 5% of gross after $3000 sales per quarter.”
   • [community] “i know games with $3 million dollar budgets that chose Unity over Unreal because with Unreal that would have cost them $150k whereas with Un…”

   proof ↗⚑ flag

   Bevy✓fullprobed9/10

   Bevy's own site explicitly states it is 100% free forever, MIT OR Apache-2.0 licensed, with no contracts, no license fees, and no sales cuts, directly satisfying the studio-lead's ask of no royalties or per-install fees. This is corroborated independently by crates.io license metadata and by community commentary praising the permissive MIT licensing as 'no strings attached.' Missing for 10: no explicit legal/contract analysis or enterprise-scale case study confirming zero royalty obligations at large studio scale.

   • [claimed-docs] “100% free. Forever and always * Open Source under the permissive MIT or Apache 2.0 licenses * No contracts * No license fees * No sa…”
   • [claimed-docs] “It is free and open-source forever under your choice of the MIT or Apache 2.0 licenses.”
   • [community] “MIT License, well done! It's so refreshing to see things released with no strings attached... a breathe of fresh air as a potential end user…”
   • [probe] “PROBE runtime (recorded 2026-09-15): bevy resolves on crates.io — `cargo search bevy` → 'bevy = "0.19.1" # A refreshingly simple data-driven…”

   proof ↗⚑ flag

Source

1. game developerRead and modify the full engine source when I hit a wall

   weight 2 · round to Bevy
   Unreal Engine✓fullprobed7/10

   Epic's license page explicitly grants 'Access to the source code' and docs describe creating new Gameplay C++ classes that recompile directly into the Editor, and community comments corroborate 'source code included.' Missing for 10: independent hands-on account of actually patching core engine internals (not just gameplay classes), and the probe notes the source repo is EULA/GitHub-account gated rather than freely open, which adds friction to the 'when I hit a wall' scenario.

   • [claimed-docs] “Access to the source code”
   • [claimed-docs] “Access to the source code All platforms & features Forums and documentation on the Epic Developer Community”
   • [claimed-docs] “Creating new Gameplay classes in C++, and all changes will be reflected in the Unreal Editor after compiling with either Visual Studio or XC…”
   • [claimed-docs] “Creating new Gameplay classes in C++, and all changes will be reflected in the Unreal Editor after compiling with either Visual Studio or XC…”
   • [community] “Crytek has financial worries. Plus it's the most difficult to use, because it's almost all C++. Unity is very accessible thanks to C# script…”
   • [probe] “PROBE runtime negative (recorded 2026-09-15): Unreal is the least machine-readable presence of the eight — api.github.com/repos/EpicGames/Un…”

   proof ↗⚑ flag

   Bevy✓fullprobed9/10

   Bevy is fully open-source (MIT/Apache 2.0), with source hosted openly, allowing developers to read and modify the engine itself; community confirms code is clean/readable and license is unrestricted ('no strings attached'). Missing for 10: no explicit hands-on account of a developer patching/forking the engine source to unblock themselves, only license and code-quality corroboration.

   • [claimed-docs] “It is free and open-source forever under your choice of the MIT or Apache 2.0 licenses.”
   • [claimed-docs] “100% free. Forever and always * Open Source under the permissive MIT or Apache 2.0 licenses * No contracts * No license fees * No sa…”
   • [claimed-docs] “Why are we continuing to build up the ecosystems of closed-source monopolies that take cuts of our sales and deny us visibility into the tec…”
   • [community] “Got the chance of running the examples and glance over the code... it looks incredibly elegant and clean. Almost feels like this could make …”
   • [community] “MIT License, well done! It's so refreshing to see things released with no strings attached... a breathe of fresh air as a potential end user…”
   • [probe] “PROBE runtime (recorded 2026-09-15): bevy resolves on crates.io — `cargo search bevy` → 'bevy = "0.19.1" # A refreshingly simple data-driven…”

   proof ↗⚑ flag

Trust

1. studio leadThe pricing and license terms have a track record of stability — no retroactive changes that reprice games already shipped

   weight 2 · round to Bevy
   Unreal Engine—none0/10

   The pack shows royalty terms changed over time (5% of gross → 5% after $3,000/quarter) but no evidence addresses whether such changes were ever applied retroactively to already-shipped titles or whether Epic has an explicit no-retroactive-repricing policy/track record. Missing for 10: documented policy or community confirmation that license terms are grandfathered for shipped games, evidence of any past retroactive-change controversy or its resolution.

   • [community] “It appears they've backed off on the royalties, too: originally, it was 5% of gross, and now it's 5% of gross after $3000 sales per quarter.”
   • [community] “For those who don't know what the deal is with Unreal Engine, there's no charge until you get the first million dollars in revenue. Then the…”
   • [claimed-docs] “Access to the source code”

   proof ↗⚑ flag

   Bevy✓fullcommunity7/10

   Bevy is licensed under MIT/Apache 2.0 with explicit 'no contracts, no license fees, no sales cuts, forever' commitments, and these are irrevocable open-source licenses that cannot retroactively reprice already-shipped games — corroborated by community praise for the license having 'no strings attached.' Missing for 10: a long multi-year track record (Bevy is a young, pre-1.0 project) and any explicit governance statement committing to never relicense future versions restrictively.

   • [claimed-docs] “100% free. Forever and always * Open Source under the permissive MIT or Apache 2.0 licenses * No contracts * No license fees * No sa…”
   • [claimed-docs] “It is free and open-source forever under your choice of the MIT or Apache 2.0 licenses.”
   • [community] “MIT License, well done! It's so refreshing to see things released with no strings attached... a breathe of fresh air as a potential end user…”

   proof ↗⚑ flag

1. ai-native userDo everything through the API that I can do in the UI

   weight 2 · round to Unreal Engine
   Unreal Engine~partialprobed5/10

   Unreal exposes substantial programmatic surfaces (Python editor scripting, C++ gameplay/engine API, Blueprints, command-line/UAT automation) that cover many editor and runtime tasks, but there is no documentation or evidence claiming full UI/API parity — some editor UI workflows (e.g. certain asset browser, viewport, or complex tooling operations) are not confirmed as scriptable, and the probe notes the engine is poorly machine-accessible overall (gated source repo, 403s on core domains, no official MCP, docs not served as markdown). missing for 10: an explicit statement/spec of full UI-API parity, evidence that every UI action has an API equivalent, and better machine-readable API discovery for AI agents.

   • [claimed-docs] “provides the ability for designers to use virtually the full range of concepts and tools generally only available to programmers”
   • [claimed-docs] “Automate time-consuming Asset management tasks in the Unreal Editor, like generating Levels of Detail (LODs) for Static Meshes.”
   • [claimed-docs] “there may be cases where you want precise control over when and how Assets are discovered, loaded, and audited. For these cases, the Asset M…”
   • [claimed-docs] “Creating new Gameplay classes in C++, and all changes will be reflected in the Unreal Editor after compiling with either Visual Studio or XC…”
   • [claimed-docs] “command-line arguments can be an invaluable tool for testing and optimizing your project”
   • [probe] “PROBE runtime negative (recorded 2026-09-15): Unreal is the least machine-readable presence of the eight — api.github.com/repos/EpicGames/Un…”

   proof ↗⚑ flag

   Bevy—none0/10

   The axis applies to this product kind (peer products hold positive or none verdicts on this story), so lack of evidence for an applicable capability is "none", never "na". (na/none harmonized at arena bring-up — see pipeline/scripts/na-harmonize.ts.)

   ⚑ flag

2. ai-native userExport all of my data in open formats and leave

   weight 3 · round to Bevy
   Unreal Engine—none0/10

   Evidence covers Blueprints, C++, plugins, source-code access, and asset management, but nothing addresses exporting a project's proprietary .uasset/.umap data into open interchange formats to allow a clean migration away from Unreal. The probe evidence even highlights poor machine-readable/open access to Epic's own ecosystem, reinforcing the lack of a data-portability story.

   • [claimed-docs] “provides a framework for managing Assets that can divide content into chunks that make sense in the context of your project”
   • [claimed-docs] “there may be cases where you want precise control over when and how Assets are discovered, loaded, and audited. For these cases, the Asset M…”
   • [probe] “PROBE runtime negative (recorded 2026-09-15): Unreal is the least machine-readable presence of the eight — api.github.com/repos/EpicGames/Un…”

   proof ↗⚑ flag

   Bevy~partialprobed5/10

   Bevy is a local, open-source Rust engine (MIT/Apache-2.0) with no cloud data lock-in, and its Scene system lets you save/load ECS worlds in the open RON format, which aligns with the openness theme. However there's no explicit documentation or tooling framed around 'exporting all your data and leaving' (e.g., data migration guides, guaranteed format stability) since Bevy isn't a hosted service holding user data in the first place. Missing for 10: explicit data-export/migration documentation, guarantees around long-term format stability given breaking API changes each release, and any first-party statement on data portability beyond the general OSS license.

   • [claimed-docs] “Create, save, and load ECS worlds using Bevy's Scene system”
   • [claimed-docs] “It is free and open-source forever under your choice of the MIT or Apache 2.0 licenses.”
   • [claimed-docs] “100% free. Forever and always * Open Source under the permissive MIT or Apache 2.0 licenses * No contracts * No license fees * No sa…”
   • [probe] “PROBE runtime (recorded 2026-09-15): bevy resolves on crates.io — `cargo search bevy` → 'bevy = "0.19.1" # A refreshingly simple data-driven…”

   proof ↗⚑ flag

3. ai-native userRead the product's source under an open license

   weight 2 · round to Bevy
   Unreal Engine!disputedcontradicted3/10

   Epic's own licensing page claims 'access to the source code' (unreal-docs-10, unreal-docs-18), but this is EULA/account-gated rather than an open-license grant — the probe confirms the GitHub source repo returns 404 without an authenticated, linked Epic account and all first-party domains block non-browser access, meaning the source is not freely readable under an open license as an AI-native user would need. Missing for 10: no OSI-approved or otherwise open license governing the source, no keyless/anonymous access to the code, no llms.txt or machine-readable confirmation of licensing terms.

   • [claimed-docs] “Access to the source code”
   • [claimed-docs] “Access to the source code All platforms & features Forums and documentation on the Epic Developer Community”
   • [probe] “PROBE runtime negative (recorded 2026-09-15): Unreal is the least machine-readable presence of the eight — api.github.com/repos/EpicGames/Un…”

   proof ↗⚑ flag

   Bevy✓fullprobed9/10

   Bevy's source and docs are explicitly MIT OR Apache-2.0 licensed, confirmed both by first-party docs and independent runtime crates.io metadata, and community commenters corroborate the open, permissive licensing and code readability. Missing for 10: no direct GitHub repo citation in the evidence pack, though license and source availability are otherwise well-documented.

   • [claimed-docs] “It is free and open-source forever under your choice of the MIT or Apache 2.0 licenses.”
   • [claimed-docs] “100% free. Forever and always * Open Source under the permissive MIT or Apache 2.0 licenses * No contracts * No license fees * No sa…”
   • [community] “MIT License, well done! It's so refreshing to see things released with no strings attached... a breathe of fresh air as a potential end user…”
   • [probe] “PROBE runtime (recorded 2026-09-15): bevy resolves on crates.io — `cargo search bevy` → 'bevy = "0.19.1" # A refreshingly simple data-driven…”

   proof ↗⚑ flag

4. ai-native userSelf-host the core product

   weight 3 · round to Bevy
   Unreal Engine~partialprobed6/10

   Unreal ships as a locally-installed engine with source-code access (unreal-docs-10/18), so the core product is inherently self-hostable rather than SaaS-only. However, the probe evidence shows source access is EULA/account-gated (must link a GitHub account to Epic), the GitHub repo is not publicly discoverable via API, and there is no simple open self-hosting path comparable to fully open-source engines. Missing for 10: unrestricted/public source access, no account-gating requirement, first-party documentation framing self-hosting as an explicit feature.

   • [claimed-docs] “Access to the source code”
   • [claimed-docs] “Access to the source code All platforms & features Forums and documentation on the Epic Developer Community”
   • [probe] “PROBE runtime negative (recorded 2026-09-15): Unreal is the least machine-readable presence of the eight — api.github.com/repos/EpicGames/Un…”

   proof ↗⚑ flag

   Bevy✓fullcommunity7/10

   Bevy is not a hosted service at all — it's an open-source (MIT/Apache-2.0) Rust library added directly as a dependency to your own project and compiled/run entirely on your own machine, satisfying self-hosting by default with no server or cloud dependency (bevy-docs-18, bevy-docs-21, bevy-docs-25). Community corroboration confirms the open license and local dev workflow (bevy-comm-2). missing for 10: explicit vendor-authored self-hosting/deployment guidance (e.g., docs discussing running Bevy apps as self-hosted servers or headless builds) and independent verification of self-hosted production deployments.

   • [claimed-docs] “It is free and open-source forever under your choice of the MIT or Apache 2.0 licenses.”
   • [claimed-docs] “Bevy is just a normal Rust dependency. You can either add it to an existing Rust project or create a new one.”
   • [claimed-docs] “100% free. Forever and always * Open Source under the permissive MIT or Apache 2.0 licenses * No contracts * No license fees * No sa…”
   • [community] “MIT License, well done! It's so refreshing to see things released with no strings attached... a breathe of fresh air as a potential end user…”

   proof ↗⚑ flag

Targets

1. studio leadOne project exports to desktop, mobile, and (directly or via partners) consoles

   weight 3 · round to Unreal Engine
   Unreal Engine~partialcommunity7/10

   Docs show a single project can be cooked/packaged/deployed to multiple target platforms via the cook/package pipeline (unreal-docs-16, unreal-docs-17) and tested across platforms via the toolbar (unreal-docs-9), and community mentions cross-platform export (e.g., HTML5) confirm this in practice (unreal-comm-14). However, the evidence pack contains no explicit documentation or independent confirmation of console export specifics (partner/licensee console SDK integration), so console support is inferred rather than directly evidenced. Missing for 10: explicit console-platform export/partner-program documentation, independent studio confirmation of a single project shipping to consoles.

   • [claimed-docs] “UnrealEditor.exe <GameName or uproject> -run=cook -targetplatform=<Plat1>+<Plat2>”
   • [claimed-docs] “This command can cook content for a platform, package it up into a platform's native format for distribution, deploys it to the device, and …”
   • [claimed-docs] “Use UE Toolbar to quickly test a part of your currently loaded Level for testing and debugging.”
   • [community] “For someone who's actually using UE4 as an artistic break for web dev, I thoroughly recommend it. It allows you to create great environments…”

   proof ↗⚑ flag

   Bevy~partialcommunity5/10

   Docs confirm one Bevy project can target desktop (Windows/macOS/Linux), mobile (iOS/Android) and Web via a single codebase [bevy-docs-6], and community feedback corroborates real-world mobile/web use [bevy-comm-10][bevy-comm-20]. However, there is no evidence—first-party or community—of console export capability, whether direct or via third-party porting partners, which is a key part of the story. Missing for 10: any mention of console targets (Switch/PlayStation/Xbox), official or partner-based console export tooling, or case studies of console shipping.

   • [claimed-docs] “Support for all major platforms: Windows, MacOS, Linux, Web, iOS, Android”
   • [community] “We support low-end devices well! Bevy runs well on iOS currently... Fans spinning is a known issue, but it is generally decoupled from frame…”
   • [community] “Man, you guys really kill it with blog/changelog announcements. Great job! For my use case, Bevy web (and mobile is nice too) support would …”

   proof ↗⚑ flag

Web

1. web developerMy game runs in the browser with a reasonable payload — WebGL today, and a credible WebGPU story

   weight 2 · round to Bevy
   Unreal Engine—none0/10

   The only evidence touching web export is a decade-old community comment noting 'UE4.7 can export to HTML5 too' (unreal-comm-14) — there is no current documentation, no mention of WebGL, no mention of WebGPU, and no discussion of browser payload size or a credible modern web-export pipeline. Given Unreal actually removed HTML5/WebGL export in later versions, this stale anecdote does not establish a current capability.

   • [community] “For someone who's actually using UE4 as an artistic break for web dev, I thoroughly recommend it. It allows you to create great environments…”

   proof ↗⚑ flag

   Bevy~partialcommunity5/10

   Bevy documents official Web platform support and showcases live wasm-compiled examples running in-browser, and a community comment shows real interest in adopting Bevy specifically for web/mobile targets. However, the evidence never mentions WebGPU explicitly, payload size/optimization guidance, or any hands-on report of browser performance/bundle size — the WebGPU 'credible story' half of the claim is unevidenced. Missing for 10: explicit WebGPU backend documentation or roadmap, payload-size/optimization guidance, and independent hands-on confirmation of web build performance.

   • [claimed-docs] “Support for all major platforms: Windows, MacOS, Linux, Web, iOS, Android”
   • [claimed-docs] “Browse bevy examples compiled to wasm and running directly in your browser!”
   • [community] “Man, you guys really kill it with blog/changelog announcements. Great job! For my use case, Bevy web (and mobile is nice too) support would …”

   proof ↗⚑ flag

2. web developerThe engine installs from a package registry into my existing toolchain — a library I import, bundle, and tree-shake like any dependency

   weight 2 · round drawn
   Unreal Engine—none0/10

   The axis applies to this product kind (peer products hold positive or none verdicts on this story), so lack of evidence for an applicable capability is "none", never "na". (na/none harmonized at arena bring-up — see pipeline/scripts/na-harmonize.ts.)

   ⚑ flag

   Bevy—none0/10

   Bevy is distributed exclusively as a Rust crate via crates.io/cargo (bevy-docs-21, bevy-probe-rt-1), not as an npm/JS package; its 'Web' platform support (bevy-docs-6) means compiling to WASM as a game binary, not shipping a tree-shakeable JS library a web developer imports and bundles. No evidence shows npm registry presence, ES-module packaging, or tree-shaking support.

   • [claimed-docs] “Bevy is just a normal Rust dependency. You can either add it to an existing Rust project or create a new one.”
   • [claimed-docs] “Support for all major platforms: Windows, MacOS, Linux, Web, iOS, Android”
   • [probe] “PROBE runtime (recorded 2026-09-15): bevy resolves on crates.io — `cargo search bevy` → 'bevy = "0.19.1" # A refreshingly simple data-driven…”

   proof ↗⚑ flag

Iteration

1. game developerThe edit-run loop is fast — hot reload or near-instant preview after a script change

   weight 2 · round to Unreal Engine
   Unreal Engine~partialclaimed6/10

   Docs confirm Blueprints allow instant in-editor scripting changes without recompilation, and C++ changes are 'reflected in the Unreal Editor after compiling' via Visual Studio/XCode, indicating a hot-reload/live-coding workflow exists. However, no evidence quantifies compile/reload speed, mentions the dedicated 'Live Coding' feature explicitly, or provides independent hands-on confirmation that the loop is fast rather than just functional. Missing for 10: benchmark/timing evidence on hot reload speed, explicit mention of Live Coding feature, independent developer testimony on edit-run loop responsiveness.

   • [claimed-docs] “provides the ability for designers to use virtually the full range of concepts and tools generally only available to programmers”
   • [claimed-docs] “Creating new Gameplay classes in C++, and all changes will be reflected in the Unreal Editor after compiling with either Visual Studio or XC…”
   • [claimed-docs] “Creating new Gameplay classes in C++, and all changes will be reflected in the Unreal Editor after compiling with either Visual Studio or XC…”

   proof ↗⚑ flag

   Bevy~partialprobed5/10

   Bevy's own docs directly claim 'instant feedback on your changes without app restarts or recompiles' and cite very fast compile times (0.8–3.0s) with a 'fast compiles' config, which matches the story's intent. However, Bevy is a Rust-native engine (not script-based), so this reload speed is achieved via build tooling/dynamic linking rather than a true scripting hot-reload workflow, and there is no independent/hands-on community confirmation of this specific edit-run loop experience — community comments focus on ECS ergonomics, docs quality, and breaking changes instead. Missing for 10: independent/hands-on verification of the hot-reload claim, clarity on scripting vs. Rust recompilation semantics, and community testimony specifically about iteration speed.

   • [claimed-docs] “Get instant feedback on your changes without app restarts or recompiles”
   • [claimed-docs] “With Bevy you can expect 0.8-3.0 seconds with the "fast compiles" configuration”
   • [probe] “PROBE runtime (recorded 2026-09-15): bevy resolves on crates.io — `cargo search bevy` → 'bevy = "0.19.1" # A refreshingly simple data-driven…”

   proof ↗⚑ flag

Language

1. game developerThe primary scripting language is productive and fully exposes the engine API, with a debugger behind it

   weight 3 · round drawn
   Unreal Engine~partialcommunity5/10

   Docs show C++ as the primary language with full engine API exposure (new Gameplay classes, delegates binding to arbitrary objects) and it compiles/reflects via Visual Studio/XCode, implying standard IDE debugger support, while Blueprints (the more 'scripting'-like option) explicitly trades off some API depth for accessibility (unreal-docs-1,2,3,11). Community evidence corroborates a productivity/API-completeness tension: Blueprints alone are 'not sufficient' for real scripting tasks and require C++ fallback, and multiple developers cite C++ as their 'main problem' with UE (unreal-comm-4, unreal-comm-7, unreal-comm-15). Missing for 10: no explicit documentation of an integrated scripting debugger workflow (only external Visual Studio/Xcode debugging is implied), and no first-party evidence that any single primary language achieves both full productivity and full API coverage without trade-offs.

   • [claimed-docs] “provides the ability for designers to use virtually the full range of concepts and tools generally only available to programmers”
   • [claimed-docs] “Creating new Gameplay classes in C++, and all changes will be reflected in the Unreal Editor after compiling with either Visual Studio or XC…”
   • [claimed-docs] “You can dynamically bind a delegate to a member function of an arbitrary object, calling the function on the object at a future time”
   • [claimed-docs] “Creating new Gameplay classes in C++, and all changes will be reflected in the Unreal Editor after compiling with either Visual Studio or XC…”
   • [community] “With no scripting support, adding content like vehicles is pretty much impossible. Blueprints are not sufficient for such a task. A few peop…”
   • [community] “My main problem with UE is C++, I don't want to even try to download files or read json in a blueprint.”
   • [community] “blueprints are great for prototyping, but once you have too much complexity in a BP it can easily cascade inefficiencies to the point it bec…”

   proof ↗⚑ flag

   Bevy~partialcommunity5/10

   Bevy uses plain Rust as its 'scripting' layer, and docs plus community comments confirm the ECS API is idiomatic, fully native Rust with no macros/lifetimes needed (bevy-docs-14, bevy-docs-20, bevy-comm-3, bevy-comm-4), which is a strong productivity/API-exposure signal. However, there is no evidence at all of a dedicated debugger or debugging workflow behind this scripting layer, and community feedback flags limited/out-of-date docs and frequent breaking changes as productivity friction (bevy-comm-14, bevy-comm-15, bevy-comm-12). Missing for 10: explicit debugger/debugging-tool evidence, confirmation of full API surface coverage beyond ECS basics, and independent hands-on accounts of debugging Bevy games.

   • [claimed-docs] “Components: Rust structs that implement the Component trait”
   • [claimed-docs] “Unlike other Rust ECS implementations, which often require complex lifetimes, traits, builder patterns, or macros, Bevy ECS uses normal Rust…”
   • [community] “I have to say the API seems to be very pleasant and simple at a glance. Kudos to the author! This pattern is a great example of how Rust ach…”
   • [community] “This is amazing. Seriously: I had a look at nearly every game engine/GUI solution in Rust and this is by far the most thought out, ergonomic…”
   • [community] “I'm put off by the limited docs. I've read the Bevy book, only takes a few minutes, and just like that I'm out of resources to turn to when …”
   • [community] “There's an unofficial complement to the docs... Unfortunately it's somewhat out of date... The effort to keep it up to date is somewhat low …”
   • [community] “Things have started to stabilize, but unless you're willing to get your hands dirty and deal with regular breaking changes, I don't yet reco…”

   proof ↗⚑ flag

Visual

1. technical artistBuild gameplay logic with visual scripting without writing code

   weight 2 · round to Unreal Engine
   Unreal Engine!disputedcontradicted6/10

   Epic's docs confirm Blueprints let designers use most programmer-level tools without code (unreal-docs-1), and this is Unreal's flagship visual-scripting system for gameplay logic. However, hands-on community reports concretely contradict full no-code sufficiency: one dev states Blueprints were 'not sufficient' for adding content like vehicles and required C++ (unreal-comm-4), and another notes complex Blueprint graphs 'cascade inefficiencies' making C++ necessary at scale (unreal-comm-15), with a third citing C++ as the main pain point when trying to avoid it (unreal-comm-7). Missing for 10: independent case studies of large shipped games built purely in Blueprints without C++ fallback, and clearer scoping of what gameplay complexity Blueprints alone can handle.

   • [claimed-docs] “provides the ability for designers to use virtually the full range of concepts and tools generally only available to programmers”
   • [community] “With no scripting support, adding content like vehicles is pretty much impossible. Blueprints are not sufficient for such a task. A few peop…”
   • [community] “blueprints are great for prototyping, but once you have too much complexity in a BP it can easily cascade inefficiencies to the point it bec…”
   • [community] “My main problem with UE is C++, I don't want to even try to download files or read json in a blueprint.”

   proof ↗⚑ flag

   Bevy—none0/10

   Bevy is explicitly a code-first, Rust-based ECS engine (bevy-docs-1, bevy-docs-14, bevy-docs-20, bevy-docs-21) with no mention of a visual scripting system or node-based logic editor anywhere in the evidence; community feedback even discusses concerns about being forced into a code editor, reinforcing the code-only workflow.

   • [claimed-docs] “All engine and game logic uses Bevy ECS, a custom Entity Component System”
   • [claimed-docs] “Components: Rust structs that implement the Component trait”
   • [claimed-docs] “Unlike other Rust ECS implementations, which often require complex lifetimes, traits, builder patterns, or macros, Bevy ECS uses normal Rust…”
   • [claimed-docs] “Bevy is just a normal Rust dependency. You can either add it to an existing Rust project or create a new one.”
   • [community] “The integrated code editor in Godot is actually something I don't like... I hope that Bevy users won't be forced to use the Bevy editor for …”

   proof ↗⚑ flag